This invention is in the field of ignition systems for fuel burning engines and more particularly in such systems wherein the igniters thereof are AC powered. Still more specifically, it is in an area of such ignition systems wherein the AC powering means have active signal generating stages which are controlled by a timer by switching the bias current in such stages on and off for each firing cycle. The invention is also in the area where such AC power is intermodulated with a Kettering type transient.
The prior art appears to be devoid of bias modulation control of ignition systems for fuel burning engines and also of AC powered systems which are transient intermodulated, and the closest prior art is summarized briefly hereinbelow.
U.S. Pat. No. 3,820,520, shows DC bias applied to transistor base inputs without any means for interrupting the base current flow. Such patent uses a separate winding of an output transformer in series with a winding of a saturable core transformer connected to contactors, to provide magnetic biasing of the output transformer. The flow of a large DC current in these windings will load down the oscillator and cause it to stop oscillation. Hence, it is clear that no interruption of DC bias current in the base circuits of the transistors is shown by this patent and further that biasing is magnetic saturation rather than electrical switching, and still further that when magnetically biased, the transistors stop oscillating due to slow-acting magnetic core saturation.
U.S. Pat. No. 3,749,973, does not show DC bias current in the transistor stages being interrupted. As in U.S. Pat. No. 3,820,520, this circuit is magnetically biased by means of DC current through a winding to saturate the transformer and stop oscillation.
U.S. Pat. No. 3,792,695 does not show DC bias current in the transistor stages being interrupted. This patent has the same main oscillator circuit as that of U.S. Pat. No. 3,820,520, and hence its operation is the same.
U.S. Pat. No. 3,808,513, likewise does not have its transistor base inputs switched to interrupt any DC bias current thereto. A winding provides magnetic saturation of a transformer when the winding is keyed with DC current to stop oscillation.
U.S. Pat. No. 3,853,106, likewise does not have its transistor base inputs switched to interrupt any DC bias current. As discussed in connection with U.S. Pat. No. 3,820,520, a winding is used to saturate the transformer and stop oscillation.
U.S. Pat. No. 3,861,369 shows only a switching means substitute for breaker points, the output of which is directly connected to a saturation winding of a saturable core transformer. The features, are best described by the patent which are similar to those described in connection with U.S. Pat. No. 3,820,520.
U.S. Pat. No. 3,847,219 shows a two transformer oscillator. One transformer is saturated by a winding having DC current flowing therethrough which stops oscillation. No DC bias current in base of the transistors thereof is interrupted. Saturation of that one transformer causes oscillation to stop.
U.S. Pat. No. 3,818,885, shows its oscillating transistor input circuits (bases) as not having an interrupted switching means therein so that no DC bias current is interrupted in the base circuits. When DC current flows through a transformer winding, the oscillator stops oscillating due to this slow magnetic biasing.
U.S. Pat. No. 3,910,246, similar to U.S. Pat. No. 3,818,885, shows its oscillating transistor input circuits uninterrupted by switching means. Also this patent has a transformer winding which functions similarly to the transformer winding of U.S. Pat. No. 3,818,885.
U.S. Pat. No. 3,913,550 does not show interruption of biasing base current of the transistors in the oscillating circuit. Its operation as far as starting and stopping of oscillation is the same as stated in connection with U.S. Pat. No. 3,820,550, also utilizing a transformer winding to saturate a transformer.
U.S. Pat. No. 3,779,226 does not show interruption of bias current in base circuits of the oscillator. Rather, as already discussed in connection with U.S. Pat. No. 3,820,520, a winding of a transformer has a DC current passed therethrough to saturate the transformer and stop oscillation of the transistor circuit.
U.S. Pat. No. 3,758,821 may be described in terms similar to the description for U.S. Pat. No. 3,847,129.
U.S. Pat. No. 3,593,696 does not show DC bias current in oscillator stages being interrupted to switch the oscillator on and off. This patent has a magnetic pulser triggering a differentiator, which triggers a multivibrator. The multivibrator applies an input to the oscillator through an amplifier. There is no showing how the square waves of the multivibrator control oscillations of the oscillator. But even if shown, and even if it is assumed that the square waves from the multivibrator circuit trigger the oscillator, such square waves are AC, and still further it is not shown where such triggering occurs in the oscillator even if by use of the square waves.
U.S. Pat. No. 3,401,327 does not show DC bias current interruption in bases of the transistors thereof. These bases are connected to a power means without any switching of power thereto. The only switching member is a transistor that short circuits a resistor during its conduction which effects a change in frequency of oscillation.
U.S. Pat. No. 3,866,107, likewise does not show interruption of DC bias current or base current to its transistors. In fact there is no DC power to the bases of either of the two transistors to enable current flow to start in such transistors.
U.S. Pat. No. 3,867,683 does not show DC bias current applied to the bases or input stages of the inverter circuit. A transformer input to such bases is provided. The transistors are controlled by phase opposing outputs from an oscillator connected to the bases of such transistors.